Electric locos and double cab

[Overmod]

At least some of the reason for early electrics being 'double cab' might have been the size and particularly the width of some of the running gear. A Pennsy DDI electric, for example, couldn't be 'seen around' from a central cab; meanwhile, it was simple enough to build the two units 'symmetrical' -- not only was the engine bidirectional, but each half was basically identical.

Much of the older power could have rather rudimentary controls at the cabs, with the actual stuff doing the control being located in cabinets in the carbodies; this might make the attraction of double-ending far more than the disadvantage of greater length and cost for two cabs.

To me, an important issue is crash protection. Boxcabs are death traps. PRR recognized that in the '30s (with the switch from the P5 to the P5a, and also with the R1, GG1 et al. from the start). There might have been some chance of survival at Gunpow in 1987 if the lead engine had been a G; none whatsoever in a beer-can AEM7.

Of course, the short hood on modern diesel locomotives -- even the 'armored' noses of some wide cabs -- aren't much protection either, but at least there's *something*. Running long-hood-forward (or running a transfer centercab) ought to be amazingly safe for head-end collisions... provided you have really good anticlimbers between the 'trailing' cab and the following units in the consist, or the train's cars. Not something I think is sufficiently advanced...

By the way, I learned that the "F" is on locomotives to establish which way the engine is facing for maintenance -- you derive 'left' and 'right' from a datum point, and that's relative to where the F is. Has nothing to do with which end of the locomotive is leading a train, or even which cab is in use at the time. If the FRA has a hand in this, it's to ensure that all locomotives that might be in interstate service are marked alike and avoid possible confusion. Wouldn't it be nice if this extended to conductors in MU cables???

[Anonymous]

Well, if you look at the B&O tunnel motors (BB-NOS units 1-3) from around 1900, they pretty much just went back and forth through the tunnel. from the station, into the tunnel, hook up to the train, and pull it through so the smoke from the steamer wouldn't congest the tunnel and get into Baltimore's streets. when you have a fair amount of trains, theres not much time for turning around at each end. These supposedly were the first american electrics, so that may have a little bit to do with it

[Randy Stahl]

BTW I am a juice fan, if I had my way the mainlines in america would be under wire.
Another thing that gives me a chuckle is were is the front end on a dual cab locomotive?
The FRA insists that an "F" be placed on the front end of the locomotive, pretty confusing giving signals.
Randy

[jchnhtfd]

Miscellany... the FL-9 was a derivative of the FP7, and had a single cab carbody, a slightly lengthened frame, and a Bo - A1A wheel arrangement (unique in the US) with the 3 axle truck carrying the extra weight of the electrical stuff.

I'm not sure that there really is a 'reason' why many -- not all -- US electrics are double cab (there are or were a number of single cab electrics -- the Virginian Rectifiers come to mind, as do the big GE units on several roads). Custom and railroad preference suggest themselves. As Randy notes, though, they don't show up on most diesels as the double cab simply isn't needed 98% of the time, and it's not cheap.

[Randy Stahl]

Good question!!!!!!I think the thinking of the time was to make the diesel locomotive like a steam locomotive. The early switch engines like the SW series or any of the little switchers had a boilerlike front end and a cab at the other. Most electrics in this country were built by GE or Westinghouse, both of them did considerable buisness abroad. A good example are the Milw little joes, these were built for the soviet union. Interestingly enough the milw single ended these motors after a time and ran pairs of them back to back or turned them on a turn table. Most RRs realized the futility of running single locomotives of any type, if that locomotive fails the train will sit. Every locomotive had to be turned at the end of each trip, big cost and big waste of time. I think having 2 cabs on a modern locomotive is a bad idea, maintaining 1 cab is tough enough ( ask an engineer) When the electrics were built they were to be a stand alone locomotive with enough horse power to handle any train with no need to MU another motor in fact alot of them didn't even have mu capability. One of my favorite exceptions to this are the monsters the Virginion RR had 2 motors back to back , I'm not sure if they were permanently together or not. The concept of push pull came from the trolley lines, inventer Frank Sprague invented MU for his beloved trolley cars. I think the real reason some US electrics had dual cabs was because GE and westinghouse insisted on it, and the reason diesels don't have dual cabs is because it is unnecessary.
Randy

[Anonymous]

Places like Washington 's Union Station it is easy for them to just pull out and hook up to a train. Then go to someplace and have to turn around

[TH&B]

A major reason is turning the electric, not every wye has wires due to cost, it may be cheaper to put two cabs on an electric then to wire up the wyes, plus diesels run in multiple more often so you can marshal a diesel back to back or you can send a diesel down a relatively unused branch to wye it more places.

ie; where at Penn Station NY can you turn an engine quickly ?

But I have seen electric motors in comuter service where the one cab end has virtualy never been used and subsiquently not upgraded in that end.

[jeffhergert]

I'm by no means any where near an expert, but let me try.
Most electric engines are carbody type engines. Most diesels are hood units. You have one of each on a train. Both trains reach the end of the line. No turning facility. You run the respective engines to the other end of the train for the return trip. The hood unit diesel can be operated rear end leading(yes the modern desktop controlled ones would be a pain). The engineer turns around in his seat and looks out a window down the long hood.
On a carbody style engine, the engineer turns around and sees a wall or maybe a door to the engine/motor room. You need a cab at the other end to operate. That's why the early carbody diesels came in sets with a cab unit semi-permenently coupled at either end.

[AltonFan]

I would imagine that putting cabs at both ends eliminated the need for turning facilities, which saved time and real estate. I also wonder if that is why the tendency changed with diesels - one set of controls is cheaper than two.

Most of the more recent electric locomotives I can think of are of the single cab configuration. I want to say the FL-9 was the last mainline electric locomotive to have dual cabs.

[locomutt]

How about thinking "wye",and no place to turn around.(or turntable)
and the cost of catenary would be out of sight.
Not sure that there is a correct answer to your question.

[Anonymous]

Thank you very much folks, but it seems to me that nobody actually answering my question. So I will scope only

QUOTE: Is there any reason why most of electric locomotives in the US has double cab as oppose to diesel locos?

Thanks!

Karn

[DSchmitt]

Early diesels were also double ended. The box cabs wrer almost identical in appearance to box cab electrics. The GM FT was a single locomotive made up of four units in the ABBA (double ended) configuration.

While we now think of the short hood of the GP as the front, initially many railroads considered the long hood the front and many early geeps were made with dual controls.

The railroads soon learned to split up the units in the locomotive for more flexibility in operation. When run multiunit the firs and last loco in the set usually face opposite directions.

[Anonymous]

Definitely to avoid the time it takes to turn a loco (well, actually, we say "motor" if it's a pure electric unit) around. Commuter trains have a control cab located in the last passenger car. When a commuter (MARC train) runs north from Washington D.C. to Baltimore, tMaryland, the motor, or, engine, is in the front. On the return trip southbound, it appears the train is running backwards. The engineer is actually sitting in the last passenger car, operating the train from there. He/she also has a set of cab signals located inside so that the train can still operate at full speed as it is being controlled from that end of the train.

[mvlandsw]

I think most were built before push-mode became popular and the double cab avoids turning at the end of runs.

[Anonymous]

Is there any reason why most of electric locomotives in the US has double cab as oppose to diesel locos? Sometimes they do push-mode anyway, so why not make it just single?

Karn[:)]